The production of multi-coated wires, i.e. those wires having a plurality of insulating coats, such as magnet wire, requires that individual wires be coated with successive coats of insulating material. This operation is performed by passing a wire through a series of dies, after immersing the wire in an enamel solution, each die having an increasingly larger diameter than the previous die. Typically, after the application of a coat of insulation, the wire requires curing and drying of the newly formed layer. This is accomplished by passing the newly coated wire through a drying and curing oven, wherein the organic solvents used to dissolve the insulating materials within the enamel are evaporated, and then curing of the insulating material is accomplished. An example of such an enamel solution comprises synthetic polymers, such as nylon, as the insulating enamel material dissolved in organic solvents, such as phenol and cresylic acid.
The wire insulating operation is usually accomplished in a wire insulating apparatus which comprises at least one coating station wherein enamel is supplied and dies are retained, followed by a drying and curing oven, commonly a tall, vertical oven.
The wire to be insulated starts at the coating station having the dies with the smallest internal diameter, the wire passes through the enamel, which may be contained in a trough or "slip", and then through the die which limits the thickness and controls the concentricity of the enamel coat. The wire then passes upward through the oven where the material is dried and cured and then after exiting the oven may be returned to a second enameling station wherein a second die having a larger internal diameter is located. Each "pass", comprising the steps of coating the wire with a coat of insulating enamel followed by drying and curing, then returning the coated wire to the next station until the wire is coated with the desired number of insulating layers. The route of the wire through a pass defines the "process path".
To facilitate this process, the dies may be contained within a "die bar", an apparatus having a generally rectangular shape and at least one die hole passing through the die bar wherein at least one die is positioned, and an internal passage communicating with one surface of the die bar and with a die hole which provides a conduit through which enamel may be supplied from an exterior source at the station and into the interior of the die bar at a point below the die. Wire at a coating station passing upward through the die bar for coating passes first through the enamel and then through the die and, upon exiting, then passes into the drying and curing oven. Advantages of the use of such die bar is that, typically, magnet wire production involves the simultaneous coating of multiple wires in a multiple pass process, and the use of die bars containing dies of successively increasing diameters located along successive stations within the wire insulating apparatus allows for the rapid production of a multitude of individual insulated wires. This method of production provides economies of scale which decrease product cost.
To utilize this method of production, it is required that at the beginning of any production run, the individual wires be first threaded through the plurality of die bars, then the die bars must be transported through the process path and individual die bars be released sequentially one to each ccorresponding station, and then fastened at each station before full scale production may be begun.
One method of locating the die bars at their appropriate successive stations is accomplished by stacking the die bars in series, threading the individual wires through each of the dies in the die bars, and transporting them along the process path by use of an apparatus such as a pair of parallel transport cables. The transport cables extend along the process path of the apparatus for all the passes through which the product wire must travel before insulation with the desired number of coats is completed. A short piece of "carrier" wire, which may be any wire sufficient to withstand the oven temperatures, is partly wrapped around one of the transport cables, then individually wrapped around the die bars so to retain their position relative to one another, and then the remaining part of the carrier wire is wrapped around the other transport cable. In this fashion, the die bars are retained in their sequential order and may be drawn through the apparatus when the transport cables are moved. As each station is approached, the transport cables may be stopped and the lowest die bar disengaged and fastened to the station. Afterwards, the carrier wire is then re-wrapped around the transport cable, the transport cables moved again forward to the next station where the next succeeding die bar may be released. This is repeated until all the die bars have been suitably positioned after corresponding stations, after which the carrier wire may be removed.
An apparatus entitled "Die Bar Carrier" disclosed in pending U.S. patent application Ser. No. 867,617, filed on May 27, 1986, by Paul E. Justus, discloses a die bar carrier having a beam portion having two notched ends and a leaf spring which is centrally and pivotally fastened to the central portion of the beam. The spring ends are fashioned so to extend between the notches in the ends of the beam to the opposite side of the beam when compressed. This apparatus provides a die bar carrier which may be utilized and retains the die bars in a more rigid position than use of the aforementioned "carrier wire". The disclosed die bar carrier is used by fastening it to the parallel transport cables by locating it between and perpendicular to both of the transport cables, then engaging the spring ends through the notches by compressing the spring, positioning the transport cables between the portion of the spring extending between the notch and beyond the bar, and then releasing the spring, so that upon release, the spring retracts to its uncompressed position until its motion is halted by virtue of the transport cables passing at the ends of the bar.
In use, the transport cables are started and, at each station, the transport spring must be disengaged and rotated to an orientation perpendicular to the bar portion of the die bar carrier so to allow the removal of the die bar carrier from between the wires which extend below the lowest die bar. The die bar may then be released and secured at the suitable station. Thereafter, the die bar carrier may be reinserted between the wire extending from the secured die bar and the lowest remaining die bar, re-rotated so to assume the locking position, and then the spring is compressed and re-attached to the parallel transport cables. This process continues until the die bars are positioned at their respective stations and, thereafter, the die bar carrier may be removed from the apparatus.
The aforementioned methods provide two workable alternative apparatus which may be used to transport die bars through a wire insulating apparatus having parallel transport cables. The latter method is preferred as it provides a structure upon which the die bars may rest when passing through the process path during the threading operation. The leaf spring does require disengagement, rotation and disentanglement as each station for a die bar is reached. However, advantages in stability and support for a die bar, or especially for a plurality of die bars, is evident during the threading operation of such an apparatus. Nevertheless, there remains a continuing need in the art for a die bar carrier having a simpler design and which allows for die bars to be disengaged and then re-attached under the next succeeding die bar at a rate faster than that possible with the subject of the Justus application.